This invention relates to power supply apparatus and more particularly to such apparatus for supplying power to d.c. loads in a recreational vehicle or the like.
Recreational vehicles (RV's) are typically equipped with electric lights, pumps and other equipment which require d.c. power to operate. To power these loads many RV's are equipped with both a storage battery and a power supply or power pack including an a.c. to d.c. power converter. The converter supplies power to the loads when an a.c. electrical outlet is available at a campsite. Otherwise, the loads are supplied with power from the battery. A battery charging circuit is usually provided so that the converter may also charge the battery. However, as the converter concurrently supplies both the battery charging circuit and any d.c. loads that are energized, the maximum power that can be supplied to the d.c. loads cannot properly exceed the capacity of the converter less the charging current drawn by the battery. For example, if the converter has a maximum current output rating of 30 amps and the charger is rated at 10 amps, only 20 amps will be available to supply the d.c. loads when the battery is discharged. However, when the battery is fully charged 30 amps can be supplied to the d.c. equipment loads. As a consequence, the power supply had to be derated so that its rated capacity for supplying the RV d.c. equipment is a value corresponding to its converter's maximum capacity less that portion of its capacity required by the charging circuit when recharging a fully discharged battery. Thus, even though the full converter output is available to supply d.c. loads within the RV, once the battery is charged, its rating had to be reduced to a fraction of that value.